Okay thanks both for your input. Other than these occasions, I never have a no crank or start problem. After the stall, it doesn't crank.

Re: fuel and spark...this time, it was below freezing when it happened. I put heet in my tank about a week ago in anticipation of the weather. I don't buy the most expensive gas (I don't buy the cheapest either) so I usually use that stuff a few times over the winter just in case. My other car is a 63 bug and I guess I got into the routine of doing it after I had a frozen line my first winter in KY.
I did my spark plugs about 3500 miles ago, and about 7500 miles before the first time.

Yesterday morning the light was off, and I went to the closest dealer (different than the one I went to before) and they told me they could run diagnostics for $100, and that if the ecm needed updating they could do that for another $50. He said there was no chance of getting it warrantied, because it's past 36000, and that there was no way to show it had anything to do with the first incident "because a lot can happen to a car in 12000 miles." He gave me an "okay, crazy lady" look and a number for GM. I called but they were closed so I did an online report/info request thing and also made a report with NHTSA.

I called the other place and they said to bring it in that they would try to flash it under warranty, but that if it didn't turn out to be that, it's $85 diagnostic charge and then whatever cost of other repairs on that. So I have an appointment there this afternoon. She said it should take an hour to an hour and a half. Hopefully that doesn't drag out into a week like last time.